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How Serious is Testicular Cancer in Dogs? An Updated Guide for 2023

Testicular tumors are the most common genital neoplasm in male dogs. The most common forms include Leydig cell tumors (LCT), seminomas (SEM) and Sertoli cell tumors (SCT).

In-depth descriptions of these tumor types are discussed in this post.

It’s thought that some cancer is caused by a variety of risk factors. They could be environmental, genetic, or hereditary.

Cryptorchid pets (pets with undescended testicles) are more likely to develop Sertoli cell tumors and seminomas. They are not, however, likely to develop interstitial cell tumors.

Testicular cancer is a complicated subject that will be explained further in this post. Keep reading and discover the clinical signs, life expectancy, and more.

Dog Breeds at Higher Risk of Testicular Cancer

Male dogs that have one or both testicles that have not descended are more likely to develop a tumor than dogs with normal (scrotal) testicles.

Tumors of descended testicles are usually benign while those still located in the abdomen are much more likely to be malignant.

Any male dog 10 years of age or over is more prone to testicular cancer. However, there are some breeds in particular that seem to be predisposed. The breeds include:

  • German Shepherd
  • Golden retrievers
  • Boxer Dogs
  • Afghan Hounds
  • Weimaraner
  • Shetland Sheepdog
  • Collies
  • Maltese
  • Labrador Retriever

Female dogs, of course, cannot develop testicular cancer. They can, however, develop something called ovarian embryonal carcinoma. This is similar to ovarian cancer in humans.

Granulosa cell tumor is one of the most frequent ovarian tumors found in female dogs.

Testicular Cancer is normally benign

3 Main Types of Testicular Cancer in Dogs

The 3 main types of testicular tumors in dogs develop from germ cells, Leydig cells, and Sertroli cells.


Cells that make sperm.


Cells that produce testosterone


Cells that help in the development of sperm.

There are 3 main types of testicular cancer in dogs that you should be aware of. These include:

Sertoli Cell Tumors

This type of testicular cancer is the most common in dogs. These will appear as a swelling in the testicles or the scrotum area.

The size of the affected testis is usually two to three times larger than those in healthy dogs. Among differential diagnosis of testicular enlargement or feminization syndrome, ICT, SCT and seminomas are prime considerations. 

Bigliardi, E, Denti, L, De Cesaris, V, et al. Colour Doppler ultrasound imaging of blood flows variations in neoplastic and non‐neoplastic testicular lesions in dogs. Reprod Dom Anim. 2019; 54: 63– 71.

In rare cases, the Sertoli cells may metastasize in the lungs, brains, abdomen or thymus.

How Sertoli Cell Tumors Affect Dogs

Sertoli cell tumors can produce estrogen. This develops into a condition known as hyperestrogenism. When this happens, a dog may develop signs of feminization. This could include:

  • enlarged mammary glands and nipples
  • pendulous sexual organ
  • hair loss
  • hyperpigmentation (or darkening) of the skin
  • Fatigue

Too much estrogen can depress bone marrow. This causes anemia and – consequently – fatigue.

Behavioral signs of a dog with excess estrogen can include:

  • squatting to urinate (rather than lift a leg)
  • reduced sex drive
  • attraction of other male dogs


Seminomas are the second most common testicular tumors found in dogs. They are very small and develop as a result of an undescended testicle. Unfortunately, they have a very high malignancy that tend to occur in older dogs.

It’s estimated that 4% to 7% of all tumors found in male dogs occur in the testicles. Seminomas account for roughly 42% of all testicular tumors. (source: Embrace Pet Insurance).

From this 42%, it’s estimated that 34% are found in undescended testicles. There is at least a 16-fold risk of developing a seminoma in cryptorchid dogs.

Breeds who develop seminomas are typically over the age of 4. These can be really hard to find on a dog and usually produce few, if any, symptoms.

If you’re very observant, however, you may notice that your dog shows some sign of pain (pulling away, flinching, vocalization) when the testicle is palpated.

At less than 2 cm, these tumors are very hard to find. Luckily, it’s rare for these tumors to metastasize and spread to other organs.

Breeders, who don’t have their dogs castrated for obvious reasons, need to take particular care.

It’s important to keep regularly scheduled appointments with a licensed veterinarian. A veterinarian who knows your dog will be able to tell what’s normal and what isn’t. Small changes can be detected by an experienced professional.

Interstitial Cell Tumors in Dogs

Interstitial cell tumors are benign (non cancerous) and are common in older dogs over the age of 10. All dog breeds (intact males) are susceptible, but there seems to be a higher occurrence in boxers.

Interstitial cell tumors in dogs are usually found through routine physical examination. In some cases, the owner may notice changes to the color, texture, or size of the involved testicle.

Leydig Cells

One type of interstitial cell tumor that is considered rare is known as the Leydig cell tumor. It is made up of cells that release testosterone within the connective tissues of the testicles.

This tumor can occur singularly or in multiples.

Luckily, this tumor is usually benign (non-spreading). They measure 1 – 2 cm in diameter and have a spherical shape. Technically, Leydig cell tumors are classified as a sex-cord stromal tumor. That means that the tumor develops from the connective tissues of the testis.

Leydig cell tumors (although rare) affect older male dogs.

How Does Testicular Cancer Progress?

Seminomas and sertoli cells generally have a less than 15% chance of spreading and interstitial cells will not spread at all.

There’s a small possibility that testicular cancer in dogs is actually a symptom of another cancer. For example, urinary tract cancers or cancers of the reproductive system may spread and reach the testicles.

The vet will need to perform a rectal check,X rays, urinalysis as well as a blood test. If the dog is cryptorchid (has an undescended testicle), a CT scan or an abdominal ultrasound may be done to check of any other affected organs.

Diagnosing Testicular Cancer in Dogs

Suspicion of testicular cancer in dogs starts with visual evidence. You or the veterinarian may notice swelling, a change of color or texture of the testicle. In addition, your veterinarian may be able to feel subtle changes that could indicate the presence of a tumor.

If there is any concern that your dog may have testicular cancer, the veterinarian will order a series of tests that could include the following:


A sonogram measures and transmits a visual representation of sound. The procedure, known as an abdominal ultrasound, can detect scrotal lesions and the abnormal or excessive presence of blood vessels. These findings may suggest the presence of a tumor.

Ultrasounds are painless and can help to identify retained or undescended testes in the groin or abdominal cavity. In addition, ultrasounds help to visual lymph nodes and assess distant metastasIs (cancer that has spread). In addition, ultrasound can help detect abnormalities of the prostate gland.

Gray‐scale ultrasonography in combination with colour and power Doppler imaging has been well accepted as an accurate technique for assessing scrotal lesions and vascularization of the testis

Bigliardi, E, Denti, L, De Cesaris, V, et al. Colour Doppler ultrasound imaging of blood flows variations in neoplastic and non‐neoplastic testicular lesions in dogs. Reprod Dom Anim. 2019; 54: 63– 71.

Physical Examination (Scrotal Palpation)

Depending on the size of the mass, this is usually the most common way that testicular cancer in dogs is diagnosed.

Rectal Palpation

Other tests might include rectal palpation to check for signs of lymph node enlargement, complete blood count to detect a decrease in white blood cells, and ultrasound.

Abdominal Radiographs

If the veterinarian suspects cancer, he/she may order an x-ray to look for any abnormal mass. This test is also useful in determining the exact location of the retained testicle. That said, it’s not usually done before surgery.

Exploratory Surgery

This type of surgery would likely only be suggested if the veterinarian suspects the tumor has spread to the lymph nodes. Keep in mind that the chance of testicular cancer spreading is very low.

Sperm Analysis

This test might sound a little extreme, but the reality is that sperm abnormalities can result from testicular tumors.

Chest X-rays

A simple chest x-ray can help determine whether the cancer has spread.


A biopsy is the removal of a small piece of tissue for evaluation under a microscope. Normally, biopsies (or fine needle aspiration) are only performed after the surgical removal of the testicle.

When done before surgery, the procedure can result in permanent damage to the testicular tissue.

Biopsy is essential after surgery to determine whether the cancer has spread or is likely to spread.

READ: Your Guide to Spleen Tumors in Dogs

Treatment Options for Testicular Cancer in Dogs

The most successful way of treating tumors in the testicles is through castration. Surgically removing a cancerous testicle can stop the progression of the disease while removing it entirely.

In the rare instances where testicular cancer has spread to other parts of the body, chemotherapy is the recommended option.

There are 3 main types of testicular tumors in dogs

The Price of Testicular Cancer Treatment

Since the treatment of testicular cancer in dogs is pretty straightforward, costs tend to be under $500 for diagnosis and under $1000 for actual treatment.

Costs can vary significantly depending on the need for advanced surgical techniques, radiation or chemotherapy.

Clinical Signs of Testicular Cancer in Dogs

Most pet owners will never be able to detect testicular cancer. This is because there are not often any obvious clinical signs. In some cases, clinical signs depend on the type of tumor and the location.

Most testicular cancers in dogs are found through a regular physical examination by a licensed veterinarian or technician. While palpating organs and the testicles, the veterinarian may discover a lump or small mass in the area.

Having an intact dog regularly checked by a veterinarian is the best way to catch disease early. Luckily, testicular cancer in dogs usually stays within that area and doesn’t easily metastasize.

Generally speaking, there are a variety of symptoms to watch for that could suggest cancer in dogs.

It’s not to say that any or all of these symptoms mean your dog has cancer. Oftentimes, there are other conditions at play that are not life threatening. Nevertheless, it’s best to pay attention and seek veterinarian advice for the following:

  • Lumps and bumps
  • Skin lesions
  • Coughing, sneezing, vomiting, or diarrhea (with or without blood)
  • Seizures (late onset)
  • Unexplained weight loss
  • Abdominal distention
  • Enlarged lymph nodes
  • Mammary tumors
  • Testicular torsion

Prognosis for Testicular Cancer in Dogs

The prognosis is quite good for dogs that develop testicular cancer. In the majority of instances, castration is highly successful thanks to the low rate of metastasis.

While surgery can be complicated for dogs with undescended testicles, the outcomes are considered excellent.

If the cancer has spread or is considered invasive, chemotherapy combined with radiation therapy is administered.

Can Testicular Cancer in Dogs be Prevented?

Unfortunately, there is no known way of preventing testicular cancer in dogs other than castration. Castration (spaying or neutering) should be discussed with a veterinarian.

Consideration should be given to the dog breed and whether the dog is more susceptible to testicular cancer.

All intact male dogs are at risk of developing testicular cancer.

For the Love of Dog

Keeping your dog healthy and happy is really easy these days. Pet insurance, CostCare, and other payment plans can help f you don’t have the money for regular checkups and diagnostic tests.

Unless you plan to ethically breed your dog, castration is the best way to prevent cancer.

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